Large flexible fabric bags for containing and transporting flowable granular or powdered bulk material such as chemicals, minerals, foodstuff, agricultural products, pharmaceutical and cosmetic ingredients and the like have been used for many years, and their use is becoming increasingly popular. This is due to their relatively low cost and the fact that when the bags are empty, they take up very little space and are relatively light in weight. When filled, the flexible bulk containers may carry 70 cubic feet or more of material and may weigh in excess of two tons.
The bags used for such purposes have to fulfill several practical requirements. It is of primary importance that the construction of the bag must be such as to sustain heavy loads but, at the same time, the bag must be adapted to be folded or collapsed when empty to a compact and preferably flat form. Frequently, because of the nature and quantity of material shipped in such bags, the bags should also be designed so that they can be easily filled with large quantities of granular and powdered bulk materials and then readily emptied of their contents. It is also desired that such bags be designed so that, when filled, they can be easily handled, and are generally free-standing and capable of being stacked vertically one upon another. To meet these requirements, the containers are frequently made of a film or sheet of a flexible generally impervious material such as polypropylene or polyethylene.
While a variety of bags and bag construction have been suggested and used as flexible bulk containers, most flexible bulk containers possess the common elements of a flexible, inextensible bag with a fill spout on top, discharge chute on or near the bottom of the bag, and a plurality of lifting straps on or near the upper edge of the bag. Variations to this base design include internal structural enhancements such as U.S. Pat. No. 5,316,387 to Polett, and improvements to the lifting and support means as found in U.S. Pat. No. 5,340,217 to Rothman, U.S. Pat. No. 5,161,853 to Polett, and U.S. Pat. No. 5,203,633 to Derby. Another line of improvements to flexible bulk containers includes the addition of internal liners such as those described in U.S. Pat. No. 5,529,393 to Polett, U.S. Pat. No. 5,649,767 to Nickell, and U.S. Pat. No. 4,390,051 to Cuthbertson. While the container discharge chute is generally located in the bottom center of the bag, the discharge chute may be located along the bottom edge of the container sidewall as described in U.S. Pat. No. 4,767,035 to Jacobi. Finally, while the flexible bulk containers generally take on a cubical shape when filled, some containers may be cylindrically shaped such as the container disclosed in U.S. Pat. No. 4,480,766 to Platt.
Although these bags and containers are common in industry, there are several shortcomings which have been encountered during the handling, transportation and storage of such flexible bulk containers. For example, the containers are generally handled by fork trucks within facilities, stored on wooden pallets, then loaded onto plywood-lined trailer trucks or rail cars for transportation. During this handling and transportation, the containers often come into contact with sharp objects such as nails, bolts, or wooden splinters from the pallets or plywood. Occasionally, the containers are even punctured by the fork truck forks themselves. Due to the flowable granular nature of the material within the containers, this material easily and quickly leaks out of a damaged container. Since the diameter of the contained material may be as fine as 50 microns, even a small hole in the container can lead to significant leakage. Leakage results in loss of material which, in the case of exotic material such as tungsten, can be quite expensive. Additionally, many customers will not accept delivery of a leaking bag, resulting in the expense of shipping the leaking bag back to its original destination. Finally, the dust generated by leaking containers results in housekeeping expenses, and can become an inhalation safety hazard to workers.
Currently, tear or puncture holes in flexible bulk containers are dealt with in several ways. The simplest method to stop leakage is to stuff a rag or sheet of flexible material into the hole. While this approach may temporarily halt the flow of material, the rag or sheet is susceptible to falling out of the hole during handling and transportation, resulting in continued leakage. Additionally, when the material is being discharged from the container, the container changes shape and, at some point, the rag or sheet tends to fall from the hole or out the container discharge chute. The rag or sheet can then result in contamination of the material or interfere with machinery during subsequent material processing. Similarly, if the outside of the flexible bulk container has picked up wooden splinters during handling and storage, the wooden splinters can fall from the container during product discharge and contaminate the process.
Another approach to stopping leakage due to tear or puncture holes in a flexible bulk container is to apply an adhesive patch over the hole. Commercial patches currently exist for this purpose, such as the Sackpatch.TM. marketed by the B.A.G..TM. Corporation. These patches are generally made of polypropylene and are applied by means of adhesive to the outside of the container over the hole. The drawback of these patches is that the container is generally dusty, particularly if the container has been leaking, and the area around the perimeter of the hole must be thoroughly cleaned for the patch to properly adhere to the container fabric. Additionally, the patch adhesive may not properly bond to the outside of the container at lower temperatures. When the material is being discharged from the container, the container changes shape and can cause the patch to become dislodged from the container. Similar to the rag or sheet drawback, the patch can fall from the hole and result in contamination of the material or interference with machinery during subsequent material processing.
Another response to flexible bulk containers which are leaking product or have been penetrated by splinters is to ship the container back to the warehouse to have the enclosed product transferred from the damaged container to an undamaged empty container.
Alternatively, the damaged container can be placed inside another larger flexible bulk container, such as the two-piece re-usable flexible bulk container disclosed in U.S. Pat. No. 35,270 to Polett. Either way, this method incurs additional shipping, handling and container costs, and can be dangerous due to the manual handling required for the transfer.
Additionally, if the contents of the damaged container are transferred to a new container, the dust generated by the transfer process results in extra housekeeping expenses and possible inhalation hazards to workers.